The present invention relates to an overhead tilting door assembly for use in buildings, particularly in large buildings.
One of the most common types of door assemblies used in large buildings includes horizontally sliding doors. The doors are supported by the floor of the building and slide in tracks along the floor. Problems arise with these doors as the tracks can accumulate ice and mud or heave to become misaligned. Consequently, these doors are often difficult to open and close. Further, these doors require storage space on either side of the opening to accommodate the door leaves in the door open position. This storage space cuts down on the width of an opening that can be provided for a given limited area of space or land.
Another type of door assembly being built in large buildings includes a fabric roll-up type door. This door assembly comprises a wide expanse of fabric suspended from the header of a building. The door is rolled up from its lower edge around a heavy pipe secured thereto. While this type of door assembly eliminates the above-mentioned problems of the sliding doors, it has other disadvantages. The header, from which the door is suspended, must be strong to withstand the tension of the fabric caused by the wind, and to prevent inward movement of the door with the wind. It is usually disadvantageous to have a large header, since it extends downwardly into the door opening and thereby decreases the height of the useable opening for a given building height. Further, the space between the underside of the header and the roof, termed the header space, is wasted. Often building heights are critically controlled, particularly at airports, so it is desirable to minimize this header space. This type of door also provides minimal insulation to a building. In harsh climates this can be a problem. Further, this type of door usually cannot be opened in high winds without damaging either the door or the header or the heavy pipe.
A number of patents have been issued for overhead tilting door assemblies wherein the door is attached to a quadrant and is tilted by forcing the quadrant to roll along horizontal supports beside the door. Exemplary of these patents are Belgian Pat. Nos. 649,849 and 665,882, British Pat. No. 414,978, German Pat. No. 869,686 and French Pat. No. 1,354,759. All of these patented devices have one common major disadvantage; they include a counterweight on the quadrants to counterbalance the weight of the door. In a large building, the weight of the door is large, and the counterweight accordingly becomes large. Accommodating such a large counterweight can increase the header space and therefore the height of the building. Also, the weight itself, and the reinforced support means required to support the weight, add to the costs of the building. Furthermore and perhaps most importantly, it is impossible, with a fixed counterweight, to balance a door against the unpredictable force of the wind. Against large doors, this variable wind force can become very large, and therefore must be taken into consideration.